A material having a volume electric resistivity of 1.times.10.sup.11.OMEGA..multidot.cm or more can be charged with accumulated charges on the surface by being rubbed with ceramics, glass, resin or the like or by causing a corona discharge or the like. A material capable of accumulating charges on a surface is referred to as an electrically chargeable material and can be applied to various uses. For example, there is an adhesion device that makes a paper, a vinyl sheet or the like adhere utilizing the electrostatic force of a charged material. In the case where a plate for placing a sheet in an OHP is made of glass, the glass and the sheet can be individually charged by rubbing the OHP sheet onto the glass strongly, thus providing an overhead projector in which an OHP sheet does not slip down from the glass surface. Similarly, adhesion of a paper, a vinyl sheet or the like to a dielectric bulletin board, a dielectric drafting board for placing a drawing paper, and a dielectric plate for placing a paper for a plotter device can be realized in the same way, thus creating convenience that, for example, an OHP sheet does not slip down during presentation, or a sheet can be placed on a bulletin board, a drafting board and a plate for placing a paper in a plotter device without using a pressure sensitive adhesive tape or magnets. Theoretically, adhesion of a paper, a vinyl sheet or the like can be realized by charging the surface via rubbing a dielectric material and by utilizing electrostatic forces of the charged material.
However, a charge being accumulated generally escapes from a material easily, since a surface charge of a dielectric material escapes into a substance in contact with the material by means of ions (for example, carbonate ions, sodium ions or chloride ions that originally are present in the air and are dissolved in adsorbed water) in adsorbed water existing on the surface of the dielectric material. This phenomenon is seen especially in the case where humidity of an atmosphere is high and the surface of a dielectric material is hydrophilic. Conventionally, an effective surface treatment in order to prevent this phenomenon for the OHP sheet or the like has not been practiced.